In a traditional communication network, a dedicated service platform is constructed for each service, respectively. In this way, service resources can be hardly converged and shared, and operators have to maintain multiple service platforms simultaneously, thus causing waste of both network setup cost and maintenance resources.
High creditability network systems are supported by optical fiber-based transport networks. With the rapid development of data services, new patterns emerge constantly, including broadband multiservice transport and end-to-end bandwidth provision etc., and traditional Synchronous Digital Hierarchy (SDH) technology, Internet Protocol (IP) technology and Ethernet technology all fail to meet the comprehensive transport and bearing requirements of the Next Generation Network (NGN), thus there is an urgent need to set up a packet-oriented transport network form with higher efficiency and flexibility to serve as a basic platform for high-capacity information transport and exchange in the future, so as to construct a unified transport network.
An ideal unified transport network should be a converged network, i.e. different applications are carried by a unified transport network, and the key to build such a converged network is an ideal transport platform which should have the following features: integration of data, circuit and optical layer transport functions; provision of rapid multiservice switching function; possession of optical transparency to adapt to possible future protocols and services; possession of topological flexibility to expand services rapidly, which is in line with the tendency of network transformation; capability of unlimited extension of network link capacity and number of nodes; application of unified management of switching layers to realize interconnection with existing transport networks; and unified operation management and maintenance to improve network availability and realize rapid fault location.
Therefore, the Internet Engineering Task Force (IETF) puts forward the concept of Multi-Layer Network/Multi-Region Network (MLN/MRN). In a Generalized Multi-Protocol Label Switching (GMPLS) network, a switching capability is defined as a region, and a converged network having multiple switching capabilities is a Multi-Region Network (MRN), e.g. an IP network based on Wavelength Division Multiplexing (WDM), while a Multi-Layer Network (MLN) is defined more broadly, not only including MRN, but also including networks having different rates under the same switching capability, e.g. different types of rates in an SDH network.
In MLN model, two types of node are defined, one type is single switching capability node which has only one switching capability, and thus all link ports on the single switching capability node have the same switching capability. The other type is multiple switching capability node which has more than two switching capabilities. The multiple switching capability nodes can be further divided into single nodes and mixed nodes, wherein although the single nodes include two switching capabilities, switching matrice having different switching capabilities are not connected by internal links. Therefore, signals cannot be transmitted between link ports of different switching capabilities. However, switching matrice having two different switching capabilities in the mixed nodes are connected by internal links, therefore signals can be transmitted between link ports of two different switching capabilities.
In order to describe the switching capability of each link port in routing accurately, RFC4202 puts forward an Interface Switching Capability Descriptor (ISCD) and defines multiple switching capabilities, e.g. Time-Division Multiplexing (TDM) Capable is used for describing the port switching capability in an SDH device while Lambda-Switch Capable (LSC) is used for describing the port switching capability in a Reconfigurable Optical Add-Drop Multiplexer (ROADM). It is put forward in RFC4202 that the ISCDs at two ends of a link may be the same or different, e.g. the ISCDs of the ports at two ends of a link between two SDH devices may be all TDM while the ISCDs of ports between a link between an SDH device and an ROADM device are TDM and LSC, respectively.
To use ISCD broadly, the meaning of ISCD is extended. ISCD is defined to have two meanings. The first meaning can be used for describing the capability for switching one port to another in the same layer, while the second meaning is to connect the local terminating capability as a data link to another layer, i.e. the adaptive capability. For the examples above, if it is a link between two SDH devices, then ISCDs of the ports at two ends of the link indicates that a SDH signal of one local port is switched to a port of another link; if it is a link between an SDH device and an ROADM device, then the ISCDs of two ends of the link commonly indicates that wavelength signals are converted into SDH signals after being terminated inversely, or SDH signals are converted into wavelength signals after being terminated.
However, using ISCDs in the MLN network model cannot represent the terminating capabilities in all scenarios, e.g. a multiple switching capability node includes an SDH device and an ROADM device at the same time. At this time, the node includes a TDM link port and an LSC link port at the same time, and if two switching matrice are connected by an internal link, then signals can be transmitted between the TDM link port and the LSC link port. However, if there is no internal link, then the signals cannot be transmitted between the TDM link port and the LSC link port. The two scenarios above cannot be distinguished only by using ISCDs on the ports. Therefore, for the former scenario, the inter-layer adaptive capability of the internal link is described by adding an Interface Adjustment Capability Descriptor (IACD) on the LSC port.
In addition, due to the specificity of the optical layer devices, in an optical layer network, the resistance of optical layer devices needs to be described. IETF puts forward the concept of Wavelength Switched Optical Network (WSON) to describe associated information of a wavelength-based network separately, including port connectivity, wavelength conversion capability and 3R regeneration capability etc.
According to existing standards and techniques, related extension has been performed in an electro-optical multi-layer network model and a WSON model, but the information extended in the prior art is not enough for the electro-optical multi-layer network, which is analyzed in details as follows:
FIG. 1 is a schematic diagram illustrating an MLN information model in the prior art. As shown in FIG. 1, the links between Digital Cross-Connection (DXC) nodes and Optical Cross-Connection (OXC) nodes are described by different ISCDs, e.g. for the link between node A and node B, the switching capability in the ISCD of port 1 is TDM, while the switching capability in the ISCD of port 2 is LSC, thus the adaptive capability between the optical-electro layers between node A and node B can be described by the ISCDs of port 1 and port 2. However, for node C, since it is a mixed node, the switching capability in the ISCD of port 4 is LSC, and the switching capability in the ISCD of port 5 is TDM. Since OXC and DXC in the node are connected by an internal link, an IACD is required to be added on port 4 to describe the adaptive capability of the internal link. Currently, a complete routing information descriptor in an MLN information model as shown in FIG. 1 includes:
Port 1: ISCD (switching capability=TDM);
Port 2: ISCD (switching capability=LSC);
Port 3: ISCD (switching capability=LSC);
Port 4: ISCD (switching capability=LSC), IACD (adaptive capability=TDM adaptive LSC);
Port 5: ISCD (switching capability=TDM);
Port 6: ISCD (switching capability=TDM);
Port 7: ISCD (switching capability=TDM);
Port 8: ISCD (switching capability=LSC);
Port 9: ISCD (switching capability=LSC);
Port 10: ISCD (switching capability=LSC);
Port 11: ISCD (switching capability=LSC);
Port 12: ISCD (switching capability=TDM);
Port 13: ISCD (switching capability=LSC), IACD (adaptive capability=TDM adaptive LSC);
Port 14: ISCD (switching capability=LSC).
Therefore, in path selection, 4 paths may be selected based on the above routing information, i.e. A-B-C-D, A-E-F-D, A-B-C-F-D and A-E-F-C-D. Meanwhile, it is assumed that port 2 and port 8 are associated with an optical transmitter and optical receiver, and the modulation mode is Differential Phase Shift Keying (DPSK). Port 11 is associated with an optical transmitter and optical receiver, and the modulation mode is Differential Quaternary Phase Shift Keying (DQPSK) during electro-optical conversion, and node C includes multiple internal links, each of which is associated with a set of optical transmitter and optical receiver, wherein the modulation mode of optical transmitters and optical receivers associated with part of the internal links is DPSK, while the modulation mode of optical transmitters and optical receivers associated with other internal links is DQPSK. It can be seen from the information above that in the 4 obtained paths, A-E-F-D is actually unavailable, and other remaining paths are not necessarily available, which is also related to internal path selection.
FIG. 2 is a schematic diagram illustrating an embodiment of a WSON model in the prior art, and corresponds to the OXC part of node C in FIG. 1, internal restriction mainly includes the following information:
Connectivity: if it is fully connected, then port 4 is connected with port 13, and port 4 and port 13 are further connected to all uplink and downlink ports (i.e. downlink port 21, downlink port 22, uplink port 23 and uplink port 24);
Wavelength conversion or regeneration capability: the accessibility of a wavelength convertor/regenerator, wavelength input range, wavelength output range, 3R regeneration capability, and the use conditions of the wavelength convertor/regenerator etc.;
Port wavelength constraint: initial wavelength range and available wavelength information.
As shown in FIG. 2, in the WSON model, the uplink ports and downlink ports do not have the information related to the optical transmitter and optical receiver. Thus, the availability of the path A-B-C-F-D and how to select an internal path cannot be obtained during path calculation.
It can be learnt from FIG. 1 and FIG. 2, for the description based on an electro-optical multi-layer network, the routing information in the current WSON and MLN is not enough. More specifically, in the current MLN model, if the network is a multi-layer network consisting of single switching capability nodes or single nodes of multiple switching capability nodes, the adaptive capability between networks of different layers can be described by different ISCDs at two ends of a link. However, if the multi-layer network includes mixed nodes, then IACD information needs to be added to link ports of service layers in the hybrid network to describe the adaptive capability between networks of different layers in the mixed nodes. Meanwhile, resistance information in the WSON network is described through extension. However, due to the specificity of the electro-optical multi-layer, when establishing a connection, an electro layer connection needs to pass through an optical layer network, then optical transmitters/optical receivers associated with the link at the edges of two sides of the optical layer network, i.e. the link configured for adaption between optical-electro nodes, need to have the same signal processing capability. Meanwhile, if wavelength consistency of bidirectional connection is required, then optical transmitters at the two sides further need to be able to tune the same wavelength. However, the information is absent in existing MLN and WSON information models. It can be analyzed from FIG. 1 and FIG. 2, the routing information above still fail to describe the electro-optical network accurately. Therefore, during path calculation, errors may be caused to the calculation result or the path calculation may not be optimized due to the lack of the information.